Stumbled on this one this evening, this is what I get for not beta testing this round: absolutely know idea that this was a problem.
If you use a Bluetooth keyboard with VoiceOver, navigation is fine, but you will find that random things happen when you start typing in to an edit field such as odd characters, spaces, newlines etc.
It seems to be very random, some users only get it now and again or like me, all the time.
Apparently Bluetooth Braille keyboards are fine.
A solution offered by Apple is to avoid pressing the Control key by itself (such as shutting VoiceOver off). When the bug appears, Control+Option (VO) plus Right Arrow to move out of the edit field, VO+Right Arrow back, repeat, and you can use the keyboard as before. Remember, just to stay away from pressing the control key by itself, and it only fix's the issue for the current editing session: so the bug will come back.